Newton’s Third LawWeek of 2/17/15Integrated Chemistry and Physics

Bell Work 1) SEATING CHART!!! Get in your seat.

2) GRAB A WORKSHEET AT THE FRONT OF THE ROOM. Start working on it.

A force is part of an Interaction Force is part of a mutual action applies to both parties involved

When a truck crashes into a car Part of the interaction is the truck exerting a force on the car The other part is the car exerting a force on the truck

Forces always occur in pairs This is called a force pair.

Newton’s Third Law The every action there is an equal and opposite reaction

OR

Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.

SAME THING, REALLY.

Which one is action or reaction? It doesn’t matter. The important thing is that they are co-parts of

a single interaction and that neither force exists without the other

Newton’s Third Law Checkpoint Which exerts more force: Earth pulling on the Moon, or the Moon pulling on Earth?

When a heavy football player and a light one run into each other, does the light player really exert as much force on the heavy player as the heavy player exerts on the light one?

Would the damage to the heavy player be the same as the damage to the light one?

A Simple Rule Action: Object A exerts a force on Object B.

Reaction: Object B exerts a force on Object A.

Action and Reaction for Different Masses What is Newton’s formula for acceleration? a=F/m

A given force everted on a small mass produces a large acceleration, while the same force exerted on a large mass produces a small acceleration

Checkpoint What is the acceleration of a 10 kg box if a 150 kg human pushes against it with a force of 12 N? What is the acceleration of the human?

A bus and a bug have a head-on collision. The force of the bus on the bug splatters the bug all over the windshield (RIP). Is the corresponding force of the bug on the bus greater, less, or the same? Is the resulting deceleration of the bus greater than, less that, or the same as that of the bug?

Systems System: any object or collection of objects that you are studying

We always need a force OUTSIDE of the system for movement

The Horse-Cart ProblemHow does a horse pull the cart?

If it pulls on the cart, the cart pulls back, right?

Which one weighs more?

At the same time the horse pushes backward against the ground, the ground pushes forward on the horse.

This outside force—the ground—is what moves the horse-cart system

Action Equals Reaction How does tug-of-war work?

It isn’t which team provides the greatest force on the rope, but which team exerts the greatest force on the ground!

Animal Locomotion How animals move

How does a fish swim?

How do giraffes run?

How do birds fly?

Bell Work1. Please get out you Newton’s Second Law Practice Problems and

your Newton’s Second Law Graphing Worksheet and prepare to turn them in.

2. On a sheet of paper, answer the following questions:a) What does Newton’s Third Law state?b) If an 2000 kg elephant pushes on a 0.1 kg mouse with 50 N

of pressure, how much pressure would the mouse exert on the elephant (assuming the mouse survives)?

c) Also assuming the mouse survives, how much would he accelerate?

d) How much would the elephant accelerate?